Carbon-sensitive pedotransfer functions for plant-available water

Authors: BAGNALL, DIANNA - Soil Health Institute; MORGAN, CHRISTINE - Soil Health Institute; COPE, MICHAEL - Soil Health Institute; BEAN, GREGORY - Soil Health Institute; CAPPELLAZZI, SHANNON - Soil Health Institute; GREUB, KELSEY - Soil Health Institute; LIPTZIN, DANIEL - Soil Health Institute; Baumhardt, Roland - Louis; Dell, Curtis; Derner, Justin; Ducey, Thomas; Dungan, Robert - Rob; Fortuna, Ann Marie; Kautz, Mark; Kitchen, Newell; Leytem, April; Liebig, Mark; Moore, Philip; Osborne, Shannon; Sainju, Upendra; Sherrod, Lucretia; Watts, Dexter; Ashworth, Amanda; Owens, Phillip

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2022
Publication Date: 2/23/2022
Citation: Bagnall, D.K., Morgan, C.L., Cope, M., Bean, G.M., Cappellazzi, S.B., Greub, K.L., Liptzin, D., Baumhardt, R.L., Dell, C.J., Derner, J.D., Ducey, T.F., Dungan, R.S., Fortuna, A., Kautz, M.A., Kitchen, N.R., Leytem, A.B., Liebig, M.A., Moore Jr, P.A., Osborne, S.L., Sainju, U.M., Sherrod, L.A., Watts, D.B., Ashworth, A.J., Owens, P.R., et al. 2022. Carbon-sensitive pedotransfer functions for plant-available water. Soil Science Society of America Journal. 86(3):612-629. https://doi.org/10.1002/saj2.20395.
DOI: https://doi.org/10.1002/saj2.20395

Interpretive Summary: There are growing concerns that as climate changes, the frequency of drought in many areas of the world may increase. The impact of drought can be decreased by increasing the water holding capacity of soils. Some studies suggest that water holding capacity (WHC) can be increased substantially by increasing soil organic carbon (SOC), but more data are needed to support this conclusion. ARS scientists from multiple locations and scientists from the Soil Health Institute's North America Project to Evaluate Soil Health Measurements related changes in SOC to the measured water content. New functions improved WHC predictions over current functions and showed that WHC increased as SOC increased, averaging 3% increase in WHC for every 1% increase in SOC across all soil texture classes. These new functions may help incentivize adoption of management practices that increase SOC and build drought resilience.

Technical Abstract: While some studies report plant-available water holding capacity ('AWHC) can be substantially increased through management-induced increases in soil organic carbon (SOC), current pedotransfer functions show negligible effects of SOC on 'AWHC. The Soil Health Institute's North America Project to Evaluate Soil Health Measurements (NAPESHM) measured water content at field capacity using intact soil cores (to capture soil structure) and changes in SOC that result from changes in management within pedons, rather than between pedons. New pedotransfer functions were created for volumetric water content at field capacity ('FC) and permanent wilting point ('PWP) for both calcareous and non-calcareous soils. The new pedotransfer functions had predictions of 'AWHC that are more accurate than Saxton and Rawls functions in non-calcareous soils and as accurate in calcareous soils when tested on samples from the National Soil Characterization database, from which the Saxton and Rawls functions were developed. Further, the new pedotransfer functions show substantial effects of SOC on 'AWHC, while the Saxton and Rawls functions show none. For an increase in SOC of 10 mg kg-1 (1 %) the new pedotransfer functions for non-calcareous soils predicted an average increase in 'AWHC of 3.0 mm 100 mm-1 (0.03 m3 m-3) on average across all soil texture classes, which is more than double previous estimates. The new pedotransfer functions for calcareous soils predicted an increase in 'AWHC of 1.2 mm 100 mm-1 associated with a 10 mg kg-1 increase in SOC on average across all soil texture classes. The new pedotransfer functions will enable stakeholders to identify scenarios where changes in soil management that result in increased SOC are likely to provide meaningful changes in 'AWHC. These new equations can help incentivize soil management practices that increase SOC and build drought resilience.